The invention relates to a method for positioning a probe card with probe needles, which have needle tips, relative to the surface of a substrate to be tested in a direction perpendicular to the surface of the substrate. In this case, a first position of the needle tips relative to the surface of the substrate is measured and stored as a separation position in such a manner that it is approached in a first positioning step, which does not measure the distance between the needle tips and the surface of the substrate, so as to produce a distance between the needle tips and the surface of the substrate. Furthermore, a second position of the needle tips relative to the surface of the substrate is measured and stored as a contact position in such a manner that it is approached in a second positioning step, which does not measure the distance between the needle tips and the surface of the substrate, until the needle tips make contact with the surface of the substrate. An image of the needle tips is recorded along at least one horizontal imaging direction, which is essentially parallel to the surface of the substrate, and is displayed.
The invention also relates to an arrangement for positioning a probe card as shown in FIG. 8 with probe needles 1, which have needle tips 3 and are arranged on the probe card 5 such that they are oriented in position. In this case, the arrangement has a substrate holder (chuck) 11, a setting (movement) device 12 for adjusting the substrate holder (chuck) 11 relative to the probe card 5, and a recording device 13 whose recording axis 14 is directed at the probe needles 1 and essentially parallel to the substrate surface 15. In this case, the setting (movement) device 12 is provided with a drive device 16 which is provided with a memory 17 that stores a contact position and a separation position.
Substrates 18 having electrically active components, for example semiconductor components, have so-called contact pads which are used to make contact from the outside by means of probe needles. Signals can therefore be applied to these semiconductor components from the outside and the reactions of the latter to these signals can be determined. It thus becomes possible to test these substrates 18. So-called probers 19 are provided for such a test.
Probe needles 1 of probers 19 are fastened either to probe holders or to probe cards 5. When probe holders are used, the probe holders are positioned on a probe holder plate 20 in such a manner that the needle tips of the probe needles are opposite the contact pads in accordance with the pattern assumed by the contact pads.
When probe cards 5 are used the probe needles 1 are fastened to just these probe cards 5 in such a manner that the needle tips 3 of the probe needles 1 are likewise opposite the contact pads in the form of the patterns assumed by these contact pads.
In order to observe the probe needles 1 when contact is being made with the contact pads, DE 103 29 792.8 (corresponding to U.S. Pat. No. 7,057,408) describes an observation device having an observation axis 14 such that the observation axis 14 runs in the gap between the free surface 15 of the wafer (substrate 18) and the holding apparatus or apparatuses 6.
These observation devices can be used to subject the probe needles 1 to precise observation. For example, precisely the extent of overdrive achieved can thus be determined and the movement in the Z direction can be set when an extent has been defined.
In this case, it is expedient for the observation axis 14 to run in an essentially horizontal manner and parallel to the free surface 15 of the wafer (substrate 18). As a result, the holding apparatuses 6 of the components or other components do not obstruct the view of the probe needles 1.
Whereas the relative distance 21 between the needle tips 3 of the probe needles 1 and the surface 15 of the substrate 18 to be tested can be set and is consequently dependent on the setting device 12 which sets this distance 21, for example a substrate clamping apparatus which carries out a movement in a direction perpendicular to the semiconductor surface (Z-direction), the absolute height 22 of the needle tips 3, that is to say the distance between the needle tips and the installation position of the probe holder, for example a probe holder plate, is dependent on the installation or the geometrical configuration of the probe holder.
The substrates 18 are normally tested in a substrate assembly, for example in a semiconductor wafer, on which a plurality of chips are arranged as substrates. In this case, a chip is positioned relative to the needle tips 3 in the lateral direction in such a manner that the needle tips 3 come to rest above the contact pads. Contact is not yet made in this case since, for the purpose of moving the chips relative to the needle tips 3, it is necessary to set a distance 21 between the needle tips and the surface of the substrate in order to avoid the needle tips scratching the surface of the substrate. Only in the test-position is the distance between the needle tips and the surface of the substrate reduced to such an extent that the needle tips 3 on the contact pads carry out a slight scratch, that is to say a slight lateral movement, on the contact pad.
After testing, the next substrate is then approached. In this case, the distance 21 between the needle tips 3 and the surface 15 of the substrate 18 is re-established, the lateral movement is carried out in order to reach the next test position, and contact is made again.
In order to increase the speed, particularly during automatic testing, the two vertical positions, that is to say the first vertical position which is referred to as the “separation position” and the second vertical position which is referred to as the “contact position”, are stored and are read out during positioning and are set using the setting device 12.
Since there are no precise details of the exact absolute height 22 of the probe needles 1, these two stored positions no longer correspond to the actual conditions after the probe card 5 has been changed. If work is then continued with the stored positions after the probe card 5 has been changed, this may result in contact being made erroneously, in the needle tips 3 grinding the surface 15 of the substrates 18 in the event of a change in position or in an excessive contact pressure and thus in the destruction of the substrate 18 or the substrate assembly.
The recording device 13 presents an image of the probe needles on a display device 2.